Make metrics reporting more flexible in waltz

[whynick1]

Waltz only uses JmxReporter. We should make it so that waltz can select different reporters, etc. GraphiteReporter.

[whynick1]

Currently, it is hardcoded to use JmxReporter. But we want JMX plus one other reporter (graphite, or whatever). To achieve that, we need to add config parameters. For example, a host name and a port number are required for GraphiteReporter.